1. Field of the Invention
The present invention relates to a wiper device for wiping the surface of a windshield, for example, of an automobile.
2. Description of the Prior Art
In general, conventional wiper devices include an arm head, an arm retainer and an arm piece. The arm head and the arm retainer are pivotally connected together via a pivot pin or shaft. The arm retainer and the arm piece are connected together by means of a rivet, an adjust screw or the like. A spring is connected between the arm head and the arm retainer to urge the arm piece and the arm retainer toward a surface of a windshield to be wiped, so that a wiper blade is held in pressure contact with the surface of the windshield.
When the conventional wiper device is operated to wipe the surface of the windshield, a slight exciting force is produced between the surface of the windshield and the wiper blade. The thus produced exciting force is transmitted to an arm system where it is enhanced due to self-excited vibration of the arm system. The self-excited vibration of the arm system eventually brings about chattering which may occur between the arm head and the arm retainer and between the arm retainer and the arm piece. Once the chattering occurs, the wiper device is unable to perform a reliable wiping operation.
To overcome the foregoing difficulties, various attempts have been made, but none of them was successful. More specifically, most of the prior attempts aimed at increasing the stiffness of the arm head, the arm retainer and the arm piece to such an extent that an exciting force produced between wiper blade and the surface of the windshield becomes minimum. In spite of such prior attempts, chattering still occurred with a limited amplitude of vibration.